The so called bio-polymers, obtained from renewable sources, form a new generation of polymers whose two main characteristics have to be: a) that oil derivatives are not part of their make up and b) that they do not cause the environmental impact like the plastics manufactured from said oil derivatives. The ideal bio-polymer will easily degrade in nature, after which its components will be reincorporated in the food chain of our planet.
The current state of the art is capable of industrially producing certain commercially useable bio-polymers, but there are still other commercial applications remaining that, due to the features necessary in these types of materials, still have to use oil derivatives.
An example of a bio-polymer is that which is obtained by means of the polymerisation of 2-hydroxy-propanoic acid (lactic acid) monomer industrially obtained by fermentation from Bacillus theroamylovorans from certain industrial waste products, such as from the glucose remaining in the molasses waste of industrial sugar plants. The lactic acid is the most economical biomonomer, industrially polymerizable for example in the presence of sulphuric acid as a catalyser.
The natural breakdown speed of the lactic acid polymer, hereinafter called polylactates and represented by the acronym PLA, is comparable to that of the ordinary vegetable materials and on occasions is very fast. In this process factors such as humidity or certain bacteria that already exist in nature play a part. On the other hand the mechanical features of the PLAs are comparable to those of certain thermoplastics produced from oil, such as polyethylene or poly (vinyl chloride).
The pure PLA usually has a relatively high crystalinity, which gives it high fragility properties. The production of thin flexible PLA films therefore needs plasticizers. But the current plasticizers of the acrylic polyadipate or diesters of certain types of polyethylenglycols used in the manufacture of thin films of polyethylene or poly(vinyl chloride) have limited compatibility with PLA and their slow eco-degradability is a disadvantage when the polymer is PLA. The combination of these circumstances means that the plastics industry cannot currently offer thin and flexible polyacetate films to the food industry.